The body of a conventional yo-yo consists of two discs firmly connected through their centers by an axle which is centrally connected to both discs, which maintains them spaced apart and parallel to each other. A string is connected to the axle in the space between the two discs.
In one modification of the conventional yo-yo the string is looped about the axle somewhat loosely, allowing the axle, and consequently the yo-yo body as a whole, to spin or rotate within this loop of the string. This type of spinning of the yo-yo body within the loop of the string, wherein the string is not being wrapped around the axle during the spinning, is referred to as "sleeping" and is described in a British Patent to Duncan, G.B. Pat. No. 392,002 and is further described in Stivers and Ennis, U.S. Pat. No. 2,629,202, in Radovan, U.S. Pat. No. 3,717,949 and in my copending U.S. patent applications Ser. No. 293,797 entitled "YO-YO WITH TWIST-RESISTANT STRING" filed Aug. 18, 1981, and Ser. No. 298,720 entitled "TAPE-SUPPORTED SLEEPER YO-YO" filed Sept. 2, 1981.
In the other most common type of conventional yo-yo the string is firmly secured to the axle of the yo-yo body, which means that spinning of the yo-yo body must be accompanied by winding of the string about the yo-yo axle, or unwinding of the string from the yo-yo axle; this is a "non-sleeper" yo-yo.
The inventor has recently patented an unconventional yo-yo which employs more widely spaced-apart discs in association with a torsion-resistant tape or ribbon; that particular patent, U.S. Pat. No. 4,290,224, relates to a yo-yo of the non-sleeping type. This invention also relates to a non-sleeping yo-yo having a tape or a string as the support means. For description purposes, the invention will be described primarily in terms of a tape support but a string support is also within the scope of the invention.
The tape-supported yo-yo may have a swivel system and holding means such as a ring at the end opposite that attached to the axle. Basically, it is operated as follows: The tape is partially or fully wound around the yo-yo axle and the end of the tape or the holding ring is held in one hand, while the body of the yoyo is held in the other hand. The body of the yo-yo is then released and falls under the influence of gravity. However, since the tape is wrapped about the yo-yo axle, this falling translational motion must be accompained by rotation of the yo-yo body about the axis of the yo-yo as the tape unwinds from the axle. By the time the yo-yo body has reached the bottom-most part of its swing, i.e. when the tape has become fully unwound, the yo-yo body has acquired considerable angular momentum which forces it to continue rotating in the same direction, thereby causing the tape to wind about the yo-yo axle in the direction opposite to that in which it was wound previously. This causes the yo-yo body to rise up along the tape again, the distance of automatic rise being inversely dependent on the amount of rotational energy dissipated by friction between the yo-yo body and the tape, and between the yo-yo body and the air. The yo-yo body can be maintained in continuous down-and-up motion by applying a gentle upward jerk to the tape just prior to the yoyo body reaching the bottom of each swing, thereby compensating for the frictional loss of energy in the rotating yo-yo. This jerk applies a torque to the yo-yo body which increases its angular momentum.
All conventional yo-yos, both "sleepers" and "non-sleepers" employ axles of circular transverse cross-section, and it appears contrary to common sense to produce a yo-yo with anything but a circular cross-sectional axle. However, as a result of extensive experimentation with a wide variety of this type of yo-yo by the inventor, it has been discovered that those particular yo-yos having a slightly non-circular cross-sectional axle operated surprisingly more smoothly than those having an axle of circular cross-section in the assembled yo-yo. Prior to this discovery, the inventor went to a considerable effort to make yo-yos having axles which were exactly circular in cross-section; and much to his surprise those yo-yos with circular cross-sectional axles performed less smoothly than those having a noncircular axle.